With the rapid development of e-business and e-bank, the Internet and the mobile communication network are more widely applied in financial transaction or online payment. In most of the transactions, the first step is to authenticate an identity of a person who requests a transaction. Identity authentication technology includes static-password authentication, dynamic-password authentication, biological-characteristic authentication and authentication via a data certificate sent by a third party, etc.
As one of the main authentication technologies, the dynamic password generated in dynamic-password authentication varies each time, thereby avoiding the password from being guessed and cracked, A dynamic token generates a dynamic password according to a static factor and a dynamic factor, where the static factor set in the dynamic token is unchangeable, and the dynamic factor which includes a time factor, times of event and/or a challenge code is changeable. The challenge code in conventional technology is applicable to a contact dynamic token or a non-contact dynamic token, where the challenge code of the contact dynamic token is sent by a host which is connected to the dynamic token, and the non-contact dynamic token transmits the challenge code by acquiring the black and white signals output by the host screen. In the conventional technology, the signal quality is affected greatly by ambient light and the brightness of a host screen, then the received voltage is affected directly by the brightness of the host screen; hence the optical signal received by the dynamic token may be inaccurate, i.e., there may be many errors in the received optical signal.